ok, so I set out to fix a small bug in roundl for 80-bit x86 floats. The final tally is four toolchain bugs (two already mentioned here, one bitfield bug on arc and a clang crash on arm because it didn't like the way I wrote a function), transitioning to a new Zephyr SDK and new Arm Toolchain for Embedded compilers. Thirty commits later, I've managed to get things working again. Phew.